Administering an injection is a process which presents a number of both mental and physical risks and challenges for users and healthcare professionals.
Injection devices (i.e. devices capable of delivering medicaments from a medication container) typically fall into two categories—manual devices and auto-injectors.
In a manual device—the user must provide the mechanical energy to drive the fluid through the needle. This is typically done by some form of button/plunger that has to be continuously pressed by the user during the injection. There are numerous disadvantages to the user from this approach. If the user stops pressing the button/plunger then the injection will also stop. This means that the user can deliver an underdose if the device is not used properly (i.e. the plunger is not fully pressed to its end position). Injection forces may be too high for the user, in particular if the patient is elderly or has dexterity problems.
The extension of the button/plunger may be too great. Thus, it can be inconvenient for the user to reach a fully extended button. The combination of injection force and button extension can cause trembling / shaking of the hand which in turn increases discomfort as the inserted needle moves.
Auto-injector devices aim to make self-administration of injected therapies easier for patients. Current therapies delivered by means of self-administered injections include drugs for diabetes (both insulin and newer GLP-1 class drugs), migraine, hormone therapies, anticoagulants etc.
Auto-injectors are devices which completely or partially replace activities involved in parenteral drug delivery from standard syringes. These activities may include removal of a protective syringe cap, insertion of a needle into a patient's skin, injection of the medicament, removal of the needle, shielding of the needle and preventing reuse of the device. This overcomes many of the disadvantages of manual devices. Injection forces/button extension, hand-shaking and the likelihood of delivering an incomplete dose are reduced. Triggering may be performed by numerous means, for example a trigger button or the action of the needle reaching its injection depth. In some devices the energy to deliver the fluid is provided by a spring.
US 2002/0095120 A1 discloses an automatic injection device which automatically injects a pre-measured quantity of fluid medicine when a tension spring is released. The tension spring moves an ampoule and the injection needle from a storage position to a deployed position when it is released. The content of the ampoule is thereafter expelled by the tension spring forcing a piston forward inside the ampoule. After the fluid medicine has been injected, torsion stored in the tension spring is released and the injection needle is automatically retracted back to its original storage position.
WO 2004/054645 A2 discloses an injection device including a housing for containing a syringe having a bore extending from an end surface, a needle communicating with the bore through the end surface and a dispensing piston movable in said bore towards said end surface so as to expel the contents of the syringe through the needle, the housing having an opening at one end through which the needle may extend, a resilient member for biassing the syringe and the needle inwardly off the housing, a first coupling element moveable towards said one end so as to move the needle of the syringe out of the opening and to move the dispensing piston of the syringe towards the end surface, a mechanism operable to release the syringe such that the needle moves inwardly off the housing,; a drive coupling for extending from said first coupling element to the dispensing piston of the syringe so as to transfer movement of said first coupling element to the dispensing piston wherein the mechanism is triggered to release the syringe and includes components to delay release of the syringe until a predetermined period after being triggered such that it can be ensured that the dispensing piston reaches the end surface before the syringe is released and/or the mechanism includes an inertial mass moveable with the first coupling element and drive coupling and a release member actuable by the inertial mass to release the syringe such that when the dispensing piston releases the end surface of the syringe and the first coupling element and drive coupling stop moving, the inertial mass continues to move so as to actuate the release member to release the syringe.
FR 2 905 273 A1 discloses an apparatus for the automatic injection of a product into an injection site, the apparatus comprising:                a container comprising an open proximate end and a substantially closed distal end and being intended to accommodate the product, and provided at its distal end with an injection needle providing an outlet port of the container,        a housing intended to accommodate, at least partially, the container, the container being movable relative to that housing between an initial position, in which the needle is contained inside the housing, an insertion position, spaced in a distal way compared to the initial position and in which the needle is exposed over a predetermined length, and an end position in which the needle is contained inside the housing,        holding means, arranged to maintain the container in the insertion position,        disabling means, arranged to release automatically the holding means and to make move the container until the end position, the apparatus furthermore including:        timing means, arranged to control the release of the holding means by the disabling means until substantially all the product contained inside the container was brought to cross the outlet port and the injection needle before the container moves to the end position.        
WO 03/097133 A1 discloses an injection device having a needle which, when the device is operated, is first caused to project, then liquid is forced out through it, and finally the needle is automatically retracted. The needle extends forwardly from a capsule that can slide longitudinally within a barrel-like body, a relatively weak spring normally maintaining the capsule and needle retracted. A more powerful spring acts oppositely on a plunger formed by rod parts which, when released, shoots the capsule forward by acting on the liquid therein, and then forces the liquid out through the projecting needle. At the end of the forward stroke the plunger and capsule are decoupled and the weak spring returns the exhausted capsule and its needle to the retracted position. A lost motion connection provided by a piston of the rod part acts as a damper in a cylinder of the rod part, to ensure that the full dose is ejected from the needle before decoupling occurs.
WO 2009/141219 A1 discloses a damper for a medicament delivery device, which device comprises a container containing medicament, a stopper arranged in said container and movable for expelling said medicament through a dose delivery means, a plunger rod having opposing proximal and distal ends and capable of acting on said stopper, and force means capable of exerting a force on said plunger rod, wherein said damper comprises a tubular sleeve having opposing proximal and distal ends; said sleeve comprises a compartment formed by a closed end wall at the proximal end of the sleeve and the proximal end of the plunger rod which is positioned in an open end at the distal end of the sleeve; and wherein said compartment comprises a sealable and resilient pad, a fluid, and at least one passage for expelling said fluid in an annular space between said sleeve and an inner wall of said container, thereby creating a dampening force, upon movement of said plunger rod.